[Bug middle-end/42722] move_by_pieces() incorrectly pushes structures to stack

[shcherbakov at daad-alumni dot de]

------- Comment #11 from shcherbakov at daad-alumni dot de  2010-02-10 12:44 -------
Ok, m32c uses "memcpy" for all block moves (4 ints is a DImode, not BLKmode).
Additionally, it supports pre-decrement addressing mode, that enables a
mutually exclusive case to the one showing the bug.
To reproduce the bug on m32c, change the following:
1. in m32c.h replace "#define HAVE_PRE_DECREMENT 1" with 0
2. Comment out "(define_expand "movmemhi"" in blkmov.md
Then, compiling the example with structure containing 5 integers produces this:
        .file   "0.c"
.text
        .global _func1
        .type   _func1, @function
_func1:
        enter   #0
        push.w  7[fb]
        push.w  5[fb]
        mova    9[fb],a0
        push.w  2[a0]
        push.w  [a0]
        push.w  4[a0]
        jsr.a   _func2
        add.w   #10,sp
        exitd
        .size   _func1, .-_func1
        .ident  "GCC: (GNU) 4.4.3"

Obviously, the push order (fp+7,fp+5,fp+11,fp+9,...) is incorrect.

Note that removing hardcoded "memcpy" call and commenting out pre-increment
support was needed ONLY to reproduce the bug normally happening on MSP430 using
a supported M32C platform.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42722